The invention relates to stabilizer mixtures, encompassing at least one alkanolamine, at least one uracil, and, if appropriate, one perchlorate salt, the mixtures being suitable for stabilizing chlorine-containing polymers.
There are many additives which can stabilize PVC. Compounds of the heavy metals lead, barium and cadmium are particularly well suited to this purpose, but are nowadays subject to criticism on environmental grounds or due to their heavy metal content (cf. “Plastics Additives Handbook”, H. Zweifel, Carl Hanser Verlag, 5th edn., 2001, pp. 427-483 and “Kunststoff Handbuch PVC” [Plastics Handbook PVC], volume 2/1, W. Becker/D. Braun, Carl Hanser Verlag, 2nd edn., 1985, pages 531-538; and also Kirk-Othmer: “Encyclopedia of Chemical Technology”, 4th ed., 1994, Vol. 12, Heat Stabilizers, pp. 1071-1091).
Processors and consumers are increasingly refusing to use these stabilizers.
Attempts therefore continue to find effective stabilizers and stabilizer mixtures which are free from lead, barium and cadmium. The intention here is also to provide a composition which has stabilizing action with respect to thermal and/or photochemical degradation and which, as a constituent of halogen-containing polymers, gives excellent initial color and also gives color stability.
A mixing specification matched to the processing method can be provided here, appropriate for the prevailing requirements, which may be based on health and safety at work, approval restrictions or process reliability. Surprisingly, this invention provides combinations of substances which are physiologically non-hazardous in plastics and which in some cases certainly do not provide satisfactory processing stability when used alone.
The applicant's specification WO 02/48249 A2 discloses compounds of the formula (I) in combination with at least one perchlorate salt. The comparative and inventive examples of this specification show that compounds of the general formula (I), used alone, do not contribute to acceptable initial color.
It has now been found that mixtures composed of a) at least one alkanolamine or one reaction product of a mono- or polyfunctional epoxide and of ammonia or of a mono- or polyfunctional dialkyl(aryl)- or monoalkyl(aryl)amine of the general formula (I), and of b) at least one uracil of the general formula (II) or, respectively, of their precursors of the general formula (III), and, if appropriate, one perchlorate salt, in particular a perchlorate of an alkali metal or of an alkaline earth metal, are particularly suitable for stabilizing chlorine-containing polymers, in particular PVC. The object set, to provide a stabilizer mixture complying with the requirements placed upon initial color, has been met via this novel combination. Further addition of a perchlorate salt, in particular a perchlorate of an alkali metal or of an alkaline earth metal, can improve the stabilization of chlorine-containing polymers, in particular PVC.
The use of other classes of amines alone without perchlorate does not give satisfactory processing stability, and in particular the initial color of the desired moldings does not differ substantially from that of an unstabilized specimen, the consequence therefore being that the requirements for good initial color and process reliability desired by processors are not met.
The β-hydroxyalkanolamines used in combination with the uracils of structure (II) or with their precursors of structure (III) can assume the function of improving initial color. This permits production of moldings with service properties complying with expectations over a prolonged period.
Surprisingly, synergistic action of the claimed combination, extending beyond the action of comparative mixing specifications comprising the individual components, has also been found in systems with perchlorate.